I have been searching this possibility for a while, but I have not found any easy free solution to allow me do this. The first thing I wanted to do was to publish to Google+ Page using Hootsuite, but I found out that this functionality is available for Enterprise accounts only, which I obviously does not have. I don’t even really want this highly priced account, because I would not found any use for that.
So the second thing I thought about was getting data from Google+ Page. Again I was not really successful. There were some tools which should transform Google+ Page to RSS feed, but they did not work, because of some changes made by Google or something.
Since Google+ API is already accessible for some time I wondered if I could write some little service which would make a RSS feed for my Google+ Page. After some hours of work I came out with the first version. I called the service Google+ RSS.
As I said I use Google+ API to access the data and because Google has some quotas to access it’s API you have to create your own API key to use Google+ RSS. So here is a How to guide to get desired RSS feed.
First of all you have to create new project using Google+ API. Go to Google APIs console and from the drop down on the left side of the page create new project. You can use whatever project name you want. I created this service because I wanted to access data for Necronomicon magazine, so I called the project Necronomicon Google+ RSS. After you click OK you should be redirected to API Access page and you should see you new API key there.

Also make sure that Google+ API is turned ON in the Services page.

Now you have the API key. That was the harder part. The second thing you have to know is Google+ profile id of your page or some other public profile. To get this go to your Google+ Page and look at the numeric part of the URL.

Thats it! Now you have all data you need to generate your Google+ RSS feed. Go too the Google+ RSS service and put API key and Google+ profile id there.

Click on the Generate RSS button. You should be redirected to the final RSS feed page. Save this URL somewhere. You can use it in any RSS client.
It’s good we can get data from Google+ page in some generic format, but we want to send them to Facebook and Twitter or others.
To accomplish this I use RSS Graffiti for Facebook and twitterfeed.com for Twitter. Those services will check your generated RSS feed in specified interval and post data to your Facebook wall or Twitter.
Note that there is access limit on Google+ RSS. You can access your generated RSS page 3 times in 30 minutes. So just have it on mind when testing. Otherwise you will have to wait 30 minutes when you reach this limit.